Reaction of clubroot-resistant genotypes of Brassica rapa, Brassica napus and Brassica oleracea to Polish Plasmodiophora brassicae pathotypes in laboratory tests

Abstract The Brassica genotypes selected for the experiments were previously found to be resistant to various Plasmodiophora brassicae pathotypes (Pb). Their interaction with pathotypes Pb2, Pb3 and Pb9 isolated in Poland was studied, using macroscopic observation for the presence of root galls, microscopic observations of P. brassicae plasmodia in the root hairs and quantitative PCR for determination of the pathogen’s quantity in plant roots and growing media. Of the Brassica genotypes studied, only B. rapa var. capitata line AABBcc was fully resistant to all the Polish pathotypes of P. brassicae. Some of the other “clubroot-resistant” genotypes tested were resistant to selected pathotypes, e.g. Brassica napus var. rapifera ‘Wilhelmsburger’ to Pb 2 and Pb3, Brassica oleracea var. capitata ‘Kilaton F1’ to Pb2 and Brassica rapa subsp. pekinensis ‘Bilko F1’ to Pb3, but were susceptible to others. B. oleracea var. capitata ‘Bindsachsener’, B. oleracea var. acephala subvar. lacinata ‘Verheul’ and B. napus var. napus ‘Mendel F1’ were moderately to highly susceptible to all Polish P. brassicae pathotypes. These results show that the classification of virulence of P. brassicae pathotypes selected in various areas differs significantly toward the same Brasssica genotypes and puts in question the practical value of pathotype classification determined with differential sets for farmers and plant breeders. Our results showed that B. rapa var. capitata AABBcc line, B. napus var. rapifera ‘Wilhelmsburger’, B. oleracea var. capitata ‘Kilaton F1’, B. rapa subsp. pekinensis ‘Bilko F1’ could be considered in Brassica breeding programmes as a source of resistance to Polish P. brassicae isolates.